Testing instrument for toothed wheels



p 1942- F. w. FRAUMANN ETAL V 2,295,206

TESTING. INSTRUMENT FOR TOOTHED WHEELS Original Filed Jan. l4, 1939 2 Sheets-Sheet l lNVEN'fOR ,7 2- m 44AM? ATTORNEY Patented Sept. 8, 1942 TESTING INSTRUMENT FOR TOOTHED WHEELS Fred W. Fraumann and Harry E. Kitchen, Buffalo, N. Y., assignors to Farrel-Birmingham Company, .Inc., Buflalo, N. Y.

Original application January 14, 1939, Serial No. 250,984. Divided and this application August 19, 1941, Serial No. 407,474

2 Claims.

This invention relates to apparatus for testing the accuracy of pinion type cutters, gears, and similar toothed devices.

This application is a division of our copending application Serial No. 250,984, filed January 14, 1939.

The invention is particularly devised for testing the cutting edges of cutters of the helical type used in the production of continuous tooth herringbone gears. As is well known in the art, such gears are often formed by the shapinggenerating process, in which a pair of cutters operating from opposite faces of the gear blank each cut helical gear formations of opposite hands, which formations are joined precisely at the median plane of the gear. The performance of such gears is dependent not only upon the degree of accuracy in tooth contour and regularity of the right and left hand groups of helical teeth, but upon an exacting similitude between the teeth of opposing groups.

This degree of accuracy is onlyobtainable when the right and left hand cutters are substantial duplicates in diametrical and tooth contourcharacteristics, and it is an object of this invention to provide a testing apparatus which may be used to measure and to compare directly a pair of such cutters. The apparatus is devised so that with a single setting it may gauge the cutting edges directly of right and left hand helical cutters, and reflect not only differences in comparative proportions of the edge profiles, but individual errors in each cutter such as those of eccentricity or faulty tooth spacing. Cutters of this type are repeatedly resharpened by grinding,

and in each instance the testing apparatus may be used as a guide for the grinding operation to indicate the necessity of minute corrections.

The apparatus is so devised that the testing procedure, in its several phases, may be performed with considerable speed and with a minimum probability of error, as more fully set forth in the accompanying specification and drawings, wherein:

Fig. 1 is a top View of the device showing a helical cutter positioned for testing;

Fig. 2 is a side view thereof with the cutter shown in section;

Fig. 3 is an end view thereof;

Fig. 4 is a top view showing a tooth division checking fixture applied to the testing head;

Fig. 5 is an enlarged section on the line 5-5 of Fig. 4;

Fig. 6 is a fragmentary View showing another embodiment of the test block.

.mountcd in the bearing 29.

The testing instrument includes a base i 9 having an accurately ground vertical bearing H at one extremity which serves to receive a shaft l2. The shaft is formed with a central flange i3 which rests on the bearing I! and which also serves as a support for the cutter G, or like toothed device undergoing testing operations. It will be initially observed that the cutter is thus positioned for testing with its bore B as a surface of reference.

The top of the base is formed with horizontal ways which slidably receive the gibs l5, Mia of ahead ll. One gib I6 is secured from above by screws l8 and handscrew I9, which screws maybe drawn up to lock the head in any desired longitudinal position. The head I! is formed with an integral vertical bracket portion 28 which carries a vertically adjustable saddle iii, the bracket portion having gibs 22, 23, and the saddle having complementary slides 2G. One gib 23 of the bracket is a loose member which is secured by a handscrew 26 for locking the saddle in various vertical positions.

The saddle is slotted, as indicated at it's, to receive a bushing 28, which, together with the adjoining portion of the saddle, is formed as a composite bearing 29 of square cross-section. A cover plate 3| is secured to the upper surface of the saddle by screws 32, and it carries adjusting screws 33 for rigidly holding the underlying bushing in position.

A test carriage C is carried by the saddle 2i, and it includes a square spindle which is slidably The rear projecting portion of the spindle is formed with a large flange 35 having a bifurcated lug 35 secured to its upper end. The spindle is axially bored to provide bearings 31 for receiving rotatably a shaft 38. Both extremities of the shaft project from the spindle 34, the right hand end being tapered and threaded as indicated by the numerals 39 and 0 to receive an anchor plate 4! and a clamping nut 42 for rigidly securing the plate to the shaft. The opposite extremity of the shaft 38 is formed with an angular head it containing a tapped hole 45. A test block it is formed to fit the head 44, and it is secur to by a screw ii. It will be observed the block is formed with a terminal zia of rack profile, so that it may engage between adjacent teeth of the cutter.

Indexing notches 48 are formed in the anchor plate 4|, while the lug 38 of the spindle flange 555 receives an index finger 49, which is pivoted, as

indicated by the-numeral 56, to enter one of the notches 48. The flange 35 additionally carries a threaded stud 5| which projects through an arcuate slot Met in the plate 4| to provide for clamping together of the plates by a wing nut 52.

A gauge 53 of the dial type is secured to the saddle 2| in such position that its anvil 53a extends horizontally rearward, where it is adapted to be engaged by a portion of the carriage C, such as the lug 36, during forward sliding movement of such assembly.

In the testing of pinion type cutters, it will be appreciated that only the actual cutting edges need be considered, as the remainder of each tooth is tapered from the cutting edges to provide tool relief and thus has no cutting function. It will therefore be apparent that when the cutter is of the helical type, as shown, the test block 46 must necessarily be disposed at an angle so that the opposing surfaces of its rack terminal 46a are in engagement with the cutting edges of adjacent teeth. The block is therefore first set to the desired gauging angle by engaging the index finger 49 in the proper notch in the anchor plate 4!, and the components of the carriage C are then clamped by tightening the wing nut 52 so that the carriage may be slid backward or forward as a rigid unit in its square bearing 29.

During the testing operation, the carriage C is moved forward to cause the firm engagement of the testing block with the flank edges of a pair of teeth of the cutter. The anvil of the gauge 53 is engaged and depressed during this procedure to cause an indication on the gauge. This indication is cancelled by setting the gauge hand to a zero reading, which reading is used as a basis of comparison for tests on the remaining teeth. The carriage is then slid rearward to disengage the cutter teeth, and the cutter is then rotated to present the next tooth gap to the test block, which is brought into contact as before. The reading on the gauge. which may be either plus or minus the original zero value, is noted and cataloged, and the operation is continued until each tooth gap is tested.

The companion cutter (not shown), which is to be compared or paired with the cutter G, is a duplicate of the cutter G, with the exception that the teeth are of opposite hand, as is Well known in the art. This cutter, when positioned on the vertical shaft l2, presents teeth of an opposed helix angle to the test block 46, which is accordingly reset by rotating the anchor plate 4! and locating the index finger 49 in the proper notch.

The notches are located so that the block 46 may thus be moved from the angular position of Fig. 1 to a symmetrical and opposing angular position relative to the vertical axis of the device.

The new cutter is then tested without altering the previous setting of the gauge, and the dial readings obtained provide a direct comparison of the diametral characteristics of both cutters. In the event the gauge readings reflect that one cutter is oversize outside the desired tolerances, it is resharpened and re-tested until it is a practical duplicate of its companion.

Aside from the comparative feature of the tests, the test of each cutter indicates individual errors such as eccentricity of the teeth in relation to the bore B and non-uniformity of profile. In its latter aspect, it will be appreciated that the engagement of opposing edges of adjacent teeth by the test block 46 gives a dial readin which may be a summation of the characteristics of both edges. Thus, if a wide range of variation is observed, the operator may instantly locate a faulty tooth or an eccentric condition, and return the cutter for possible correction. By this means only cutters of uniform characteristics are accepted for pairing, thus assuring the production by such cutters of herringbone gears having uniform tooth contours and perfectly matched right and left hand helices.

The horizontal adjustment of the head I! and the vertical adjustment of the testing saddle 2| provides means for positioning the carriage C for testing cutters of various diameters and face width, while the notches in the angle plate permit angular adjustment of the test block to the several standard helix angles.

In Figs. 4 and 5 a division checking attachment is shown applied for use in conjunction with the described device. The attachment consists of a bracket 60, secured by screws 6| to the front of the saddle 2|, and carrying a dial gauge 62, whose anvil 62a is disposed laterally. The described test block 46 is removed for this test, and a bracket member 63 substituted therefor. This member is formed with a rigid projecting jaw 64 which is properly located to engage tangentially one tooth edge, and it is also formed with a transverse bearing 66 terminating in a split and threaded clamping barrel 6? having a tapered extremity 68. A rod H1 is received in the bearing 66 and it may be locked in any desired axial position therein by a clamping nut 7| which engages over the'threaded extremity of the barrel 61.

A second jaw 12 is formed with a hub 13 which is bored to encircle loosely the rod 10, and it is provided with opposed pivot screws '14 which engage in conical bearing seats 75 in the rod (Fig. 5). The jaw 12 is thus mounted for an arcuate or vane-like movement on the rod, and it is formed with a surface 11 which is adapted to engage tangentially the corresponding flank edge of an adjacent tooth.

It will be understood that the test performed with the aid of the attachment of Fig. 4 is supplemental to the first described tests. In other words, when a cutter has satisfactorily passed the first rigid test, there is still a possibility of error which may evade the first test as the result of a coincidence of errors, or compensating errors on opposing flank profiles. The attachment provides against this condition by checking the regularity of adjacent teeth on common flanks.

In the operation of the attachment, the carriage assembly is operated as before to bring the fixed jaw 64 into contact with a flank edge with, however, the difference that the forward movement is manually controlled until a zero reading is obtained on the first dial gauge 53. The jaw 12', in the meantime, being under spring pressure of the anvil 62a of the attachment gauge 62, is maintained against the flank edge of the adjoining tooth. This gauge is also set to a zero reading and the test proceeds tooth by tooth in an attempt to discern appreciable errors of spacing.

The testing device will be found to be equally effective in use on straight tooth cutters, especially those which require comparative accuracy, such as multiple or gang cutters. For

\ such use, the testing block 46 is retained throughscription that different modifications and arrangements of the test blocks may be made, depending upon the type of toothed device being tested. In fine pitch cutters or gears, for example, the block 46 may be made to straddle several teeth, if desired. In Fig. 6 two teeth 83 of the cutter are straddled by the tines SI of a test block 82.

The invention is therefore not to be considered as limited to the precise arrangements of the drawings, but is to be construed in the light of the following claims.

We claim:

1. A measuring instrument for determining the divisional spacing of the teeth on the periphery of a substantially cylindrical gear or cutter member comprising a mounting shaft for the member, a carriage mounted in spaced relation to said shaft, said carriage being slidable to and away from the axis of the shaft in a direction lateral thereto, a test block mounted on the carriage and adapted by the movement of the carriage to be brought adjacent the teeth, said test block having a fixed jaw and a movable jaw, said fixed jaw being of less thickness than the spacing between adjacent teeth whereby said jaw may contact one tooth only along the flank edge thereof, said movable jaw being spaced from the fixed jaw and having a gauge surface adapted to engage the corresponding portion of an adjacent tooth, and means operated by engagement of the movable jaw with said corresponding portion to indicate the deviations in spacing between successive teeth.

2. In a measuring instrument for determining the regularity of spacing of teeth on the periphery of cutters and gears, a mounting shaft for the cutter or gear to be examined, a carriage mounted in spaced relation to the shaft and including a head laterally movable toward and away from the mounting shaft axis, a test block mounted on the carriage adjacent the teeth to be examined, said block including a fixed jaw, a movable jaw, and a rod for carrying the movable jaw a predetermined distance from the fixed jaw, said rod being adjustable to vary said distance, the movable jaw being pivotally mounted on the rod on an axis substantially parallel to the mounting shaft, both of said jaws being relatively thin compared to the distance between adjacent teeth whereby contact may be made'on one surface only of the teeth, and means operated by the engagement of the jaws with corresponding portions of diiferent teeth to indicate variations in the spacing of the teeth.

FRED W. FRAUMANN. HARRY E. KITCHEN. 

